Add missing break statement in order to prevent the code from falling
through to case CB_TARGET_MASK.
This bug was found thanks to the ongoing efforts to enable
-Wimplicit-fallthrough.
Fixes: dd220a00e8 ("drm/radeon/kms: add support for streamout v7")
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>